20721049 has 4 divisors (see below), whose sum is σ = 20848336. Its totient is φ = 20593764.

The previous prime is 20721047. The next prime is 20721053. The reversal of 20721049 is 94012702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20721049 - 2¹ = 20721047 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20721047) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63399 + ... + 63724.

It is an arithmetic number, because the mean of its divisors is an integer number (5212084).

Almost surely, 2^20721049 is an apocalyptic number.

It is an amenable number.

20721049 is a deficient number, since it is larger than the sum of its proper divisors (127287).

20721049 is a wasteful number, since it uses less digits than its factorization.

20721049 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127286.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 20721049 is about 4552.0378952728. The cubic root of 20721049 is about 274.6653737005.

The spelling of 20721049 in words is "twenty million, seven hundred twenty-one thousand, forty-nine".